Duplex stainless steel of type UNS S32101 and ferritic stainless steel of type AISI 430 subjected to cathodic hydrogenation

This work presents a study on the duplex stainless steel UNS S32101 and ferritic AISI 430 when subjected to cathodic hydrogenation, to ascertain their behavior under the action of hydrogen. Throughout the research, with the aid of optical (MO), scanning electronics (SEM) and atomic force (AFM) microscopy, both hydrogen embrittlement and pitting corrosion after hydrogenation and degassing in UNS S32101 duplex stainless steel became evident. Subsequently, the X-ray diffraction performed to verify the phase transformations confirmed the transformation of the austenitic phase into the martensitic phase in the duplex steel and confirmed the formation of Cr23C6 precipitates in the ferritic steel. And so, it corroborated with the SEM images, proving the transformation of σ-phase agent of pitting corrosion in duplex steel.

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Influence of Sigma Phase Precipitation on Pitting Corrosion of 2507 Super-Duplex Stainless Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.658.380 ◽

2010 ◽

Vol 658 ◽

pp. 380-383 ◽

Cited By ~ 4

Author(s):

Ying Han ◽

De Ning Zou ◽

Wei Zhang ◽

Jun Hui Yu ◽

Yuan Yuan Qiao

Keyword(s):

Stainless Steel ◽

Corrosion Resistance ◽

Ambient Temperature ◽

Duplex Stainless Steel ◽

Pitting Corrosion ◽

Super Duplex Stainless Steel ◽

Phase Precipitation ◽

Pitting Potential ◽

Σ Phase ◽

Pitting Corrosion Resistance

Specimens of 2507 super-duplex stainless steel aging at 850°C for 5 min, 15 min and 60 min were investigated to evaluate the pitting corrosion resistance in 3.5% NaCl solution at 30°C and 50°C. The results are correlated with the microstructures obtained with different aging time. The precipitation of σ phase remarkably decreases the pitting corrosion resistance of the steel and the specimen aged for 60 min presents the lowest pitting potential at both 30°C and 50°C. With increasing the ambient temperature from 30°C to 50°C, the pitting potential exhibits a reduction tendency, while this tendency is less obviously in enhancing the ambient temperature than in extending the isothermal aging duration from 5 to 60 min. SEM analysis shows that the surrounding regions of σ phase are the preferable sites for the formation of corrosion pits which grew up subsequently. This may be attributed to the lower content of corrosion resistance elements in these regions formatted with σ phase precipitation.

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Heat Treatment Effect on Pitting Corrosion of Super Duplex Stainless Steel UNS S32750 GTA Welds

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.746.467 ◽

2013 ◽

Vol 746 ◽

pp. 467-472 ◽

Cited By ~ 1

Author(s):

In June Moon ◽

Bok Su Jang ◽

Jin Hyun Koh

Keyword(s):

Heat Treatment ◽

Stainless Steel ◽

Duplex Stainless Steel ◽

Pitting Corrosion ◽

Super Duplex Stainless Steel ◽

Σ Phase ◽

Gas Tungsten Arc ◽

Weld Metals ◽

Pitting Corrosion Resistance ◽

Heat Treated

The purpose of this study was to investigate the effect of heat treatment (930°C, 1080°C, 1230°C) followed by quenching on the pitting corrosion resistance, sigma phase precipitation, and microstructural change of a super duplex stainless steel (UNS S32750) welds made by gas tungsten arc (GTA). Based on the microstructural examination, the σ phase was formed in welds heat treated at 930°C while there were little σ phases formed in welds experienced the relatively fast cooling from 1080°C and 1230°C. Accordingly, the most weight loss due to pitting corrosion occurred in the as received base and weld metals heat treated at 930°C. It was confirmed that the pitting corrosion occurred in the phase boundaries of ferrite/sigma and austenite/sigma.

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